The present invention relates generally to a screw anchor apparatus for use in underpinning and tiebacks and, in particular, to a modular helical anchor.
Helical anchors are well known. Helical anchors are utilized in the geotechnical industry to anchor building foundations in unstable soil and to stabilize and/or repair the integrity of existing foundations and the like. A typical helical anchor is part of an assembly that consists of at least one elongated shaft member having at least one helical plate member attached thereto and extending therearound. The helical plate member is fixedly attached to the shaft member and the assembly is mounted in the ground for securing to a foundation or the like. Typically, the helical plate member is placed in the ground and the helical anchor assembly is rotated about the longitudinal axis of the shaft member, which enables the helical plate member to engage with the ground material, drawing the entire assembly into the ground to form, typically with a plurality of other anchor assemblies, a firm anchor point for the foundation. The anchor assemblies can be utilized under compression, known in the art as underpinning, wherein the anchor assembly supports a body by absorbing a compression load between opposed ends, one of which is attached to the ground and the other of which is attached to the body. The anchor assemblies can also be utilized under tension, known in the art as a tieback, wherein the anchor assembly retains the body to the foundation by applying a tension load to the opposed ends thereof.
It is common for the helical anchor assembly to vary in length, depending on the different requirements of the particular installation. Typically, the length of the helical anchor is varied by attaching a plurality of shaft members end to end, with each of the shaft members having at least one helical member attached thereto, to form an elongated anchor assembly. The shaft members are typically required to be attached by welding at the job site when the helical anchor assembly is installed, which is disadvantageously time-consuming and expensive. In addition, the helical anchor assemblies are often installed in tight quarters, which makes welding the shaft members particularly difficult.
It is desirable, therefore, to provide a helical anchor assembly that is modular in design for modifying the length of the assembly for the requirements of each installation. It is also desirable to provide a helical anchor that may be assembled, utilized, and installed in tight quarters.